The present invention relates to the field of motor vehicle navigation systems, and in particular to a motor vehicle navigation system that includes a modular display computing system for presenting navigational data to a motor vehicle user.
Navigation systems are increasingly being used in motor vehicles. These systems generally include: (i) a control unit for entering the starting location, any intermediate destinations, and the final destination; (ii) a data medium for storing navigational data (e.g., information to display road maps); (iii) a navigation computer to plan/compute the route and provide guidance to the destination; (iv) a data processing unit to process the route data into picture information; and (v) a display to display road maps, position information, destination information, etc. The navigation system also includes a plurality of sensors to determine the vehicle's position, speed, orientation, etcetera and provide that information to the navigation computer. The individual components of the navigation system communicate over a data bus. The data processing unit often includes a picture memory that stores picture information.
U.S. Pat. No. 5,689,252 entitled “Navigation System for an Automotive Vehicle” discloses a navigation system that includes a data input device, a GPS signal receiver, a direction sensor, a distance sensor, and a traffic information receiver. Data from these components are input to a microcontroller that plans the route. The microcontroller retrieves map information (e.g., road maps) from a CD-ROM. The route data computed by the microcontroller are then displayed on a CRT, which is also connected to the microcomputer. Notably, road map information cannot be displayed directly, but first must be transformed by the microcontroller into picture information suitable for presentation on the CRT.
Newer navigation units provide the user with the ability to select the picture section for displaying, using for example zoom or scroll functions. In addition, information indicative of the direction and motion of the motor vehicle are frequently shown on the road maps appearing on the display. User commands (e.g., zoom and/or scroll) and system demands (e.g., vehicle motion) regularly change the display picture information, and thus the display picture information must be continuously updated in order to present the user with accurate information indicative of the current motor vehicle position.
Prior art navigational systems require that road map information be retrieved by the navigation computer for each displayed picture and placed into intermediate storage in the picture memory.
Published European patent application EP 0 306 088 A1 entitled “Vehicle Navigation Device with Reproduction of a Selected Map Element According to a Predetermined Representation Standard” discloses a new generation navigation device. In this navigation device, the individual components are connected over a data bus. Such a linkage is customary in so-called linked driver information systems. The advantage of such linked driver information systems is that a plurality of individual components can be linked to the data bus line. For example, a display may be used not only to display navigation data, road maps, etc., but, for example, can also indicate a defect in the vehicle or the like.
The navigation device described in the published application EP 0 306 088 A1 includes a data bus, a data memory in which a large number of road maps and navigation data are stored, a navigation computer to plan the route, and a data processing unit that processes data into picture information. The data processing unit includes a picture memory to store the picture information. The navigation device also includes a display, connected to the data processing unit, to display picture information, and a communication block with a control unit for entering the starting position, intermediate destinations, and/or the final destination.
In such a system, the picture information of each road map is loaded individually into the picture memory. Such picture information is always transferred over the bus line. If the user wants to change, for example, the current screen display or if the motion of the vehicle causes picture information to change, road map information must be transferred from the data memory to the picture memory to provide the proper data for display. For a screen display with sufficient picture refresh cycles, the data bus must have a large bandwidth, which generally often not available. An additional problem is that the data bus is needed almost exclusively for transferring picture information, and therefore other information or data cannot be transferred, or can be transferred only serially during the remaining interim times.
Furthermore, a continuous and thus flowing display of geographical contents is not assured, because the screen shows only the data transferred over the data bus, and the data capacity that can be transferred on the bus is limited. Because the capacity of the bus is limited and because of the bus latency times, scroll or zoom operations, for instance, often cause dramatic picture changes that are perceived as troublesome by the viewer.
A problem with these prior art systems is that the geographical map for the display is calculated by the navigation computer. The data for the complete map to be displayed are transferred into a planar coordinate system corresponding to the display surface and are then sent by the navigation computer over the data bus to the display. With previously known systems, the monitor operates passively (i.e., only the received data are visualized). That is, there is no “intelligent” processing of the received data.
Therefore, there is a need for an improved motor vehicle navigation system.